Assertion: A p-n junction with reverse bias can be used as a photodiode to measure light intensity Reason: In a reverse bias condition the current is small but is more sensitive to changes in incident light intensity.

Question

Assertion: A p-n junction with reverse bias can be used as a photodiode to measure light intensity Reason: In a reverse bias condition the current is small but is more sensitive to changes in incident light intensity. (A) If both assertion and reason are true and reason is the correct explanation of the assertion (B) If both assertion and reason are true but reason is not the correct explanation of the assertion (C) If assertion is true, but reason is false (D) Both assertion and reason are false statements

Tardigrade Admin · Accepted Answer

Photo-diode is a reverse biased p-n junction diode as shown in figure. At the p-n junction there exists a junction field which at

equilibrium, does not permit the flow of charge carriers across the junction. When such a p-n diode is illuminated with light photons having energy h v>Eg and intensities I 1, I 2, I 3, etc., the electron and hole pairs generated in the depletion layer (or near the junction) will be separated by the junction field and made to flow across the junction. There would be a change in the reverse saturation current as shown in figure. Hence, a measurement of the change in the reverse saturation current on illumination can give the values of the light intensity.

Q. Assertion : A p−n junction with reverse bias can be used as a photodiode to measure light intensity Reason : In a reverse bias condition the current is small but is more sensitive to changes in incident light intensity.

If both assertion and reason are true and reason is the correct explanation of the assertion

If both assertion and reason are true but reason is not the correct explanation of the assertion

If assertion is true, but reason is false

Both assertion and reason are false statements

Q. Assertion : A $p - n$ junction with reverse bias can be used as a photodiode to measure light intensity
Reason : In a reverse bias condition the current is small but is more sensitive to changes in incident light intensity.